Electrical hair-cutting apparatus

ABSTRACT

A hair-cutting apparatus is provided which has an external cutting member ( 1 ) and an internal cutting member ( 7 ) which is drivable relative to the external cutting member. The external cutting member has lamellae ( 3 ) between which hair-entry apertures ( 4 ) are formed, and the ends of the lamellae form teeth ( 9 ) for raising hairs before the hairs are cut. To increase the efficiency of hair catching the teeth are given different lengths. Preferably, there are long teeth ( 9   a   , 9   b ) and short teeth ( 9   1   , 9   2 ) which alternate with one another.

FIELD OF THE INVENTION

The invention relates to an electrical hair-cutting apparatus having anexternal cutting member and an internal cutting apparatus which isdrivable relative to the external cutting member, which external cuttingmember is formed by a first wall portion, which constitutes a cuttingface, and at least a second wall portion, which is disposed at an anglewith respect to the first wall portion, which first wall portion haslamellae between which elongate hair-entry apertures are situated, endsof the lamellae extending beyond the second wall portion in such amanner that the ends of the lamellae form a row of teeth for raisinghairs before they are severed by cooperation between the cuttingmembers.

BACKGROUND OF THE INVENTION

A hair-cutting apparatus of the type defined in the opening paragraph isknown from JP-A-62/246396. The teeth at the ends of the lamellae serveto facilitate the entry of hairs to be severed into the hair-entryapertures between the lamellae. In practice, it appears that partly thehairs are not caught between the teeth but are flattened and, as resultof this, do not enter into the hair-entry apertures.

SUMMARY OF THE INVENTION

It is an object of the invention to improve the hair-catching efficiencyof the hair-cutting apparatus of the type defined in the openingparagraph. To this end, the hair-cutting apparatus in accordance withthe invention is characterized in that the teeth have differentprojecting lengths with respect to the second wall portion.Surprisingly, it has been found that this results in more hairs beingcaught per cutting movement, i.e. during an average length of movementof the cutting apparatus over the skin. This can be explained from thefact that the distance between two teeth having a great projectinglength (long teeth) is now larger, as a result of which hairs which lieflatter on the skin can be raised. Once such a hair has been lifted thishair can subsequently be raised further and guided into a hair-entryaperture (gap) by a tooth having a smaller projecting length (shorttooth). If all the teeth would have the same length such a hair, whichlies comparatively flat, could not be raised but would be flattenedunder the tooth. If in a situation that all the teeth have the samelength the distance between the teeth would be made, for example, two orthree times as large, this essentially leads to an increased chance ofmore flat-lying hairs being raised. However, to sever hairs the width ofthe hair-entry aperture (gap) between the lamellae should be withingiven limits. This width cannot be chosen to be, for example, twice aslarge in view of the protrusion of the skin in the hair-entry aperture.Increasing the distance between the teeth would then be possible only,for example, by leaving out every second tooth. In that case there arelamellae whose ends do not terminate in a tooth but which end near thesecond wall portion. As a result of this, a hair raised by a tooth isnot guided properly into the hair-entry aperture because this hairstrikes against the second wall portion near the lamella without a toothand is subsequently flattened underneath the lamellae. It is thereforedesirable that at least most lamellae, preferably all lamellae, end in atooth. By using both long and short teeth, for example alternately, thelikelihood of catching is increased and, as a result, the cuttingperformance is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with reference to anexample of a hair-cutting apparatus shown in the drawings, in which onlythe cutting section is shown. In the drawings:

FIG. 1 is a diagrammatic perspective view of a double-action cuttingapparatus in accordance with the invention,

FIG. 2 is a detailed view of a prior-art cutting apparatus whose teethall have the same projecting length,

FIG. 3 shows the cutting apparatus of FIG. 1 in a detailed view similarto that of FIG. 2,

FIG. 4 is a longitudinal sectional view of a tooth in a firstembodiment,

FIG. 5 is a longitudinal sectional view of the tooth in a secondembodiment,

FIG. 6 is a longitudinal sectional view of the tooth in a thirdembodiment, and

FIG. 7 is a plan view of a hair-cutting apparatus constructed as atriple-head shaver having circular shaving heads.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The cutting section 1 of a hair-cutting apparatus shown in FIG. 1 has aU-shaped external cutting member 1 comprising a first wall portion 2with a plurality of lamellae 3 between which elongate hair-entryapertures 4 are formed. The upper surface of this wall portion 2 formsthe cutting face 5, which is in contact with the skin during shaving. Atopposite sides of the wall portion 2 the cutting member 1 has a secondwall portion 6 which is disposed at an angle relative to the first wallportion 2 and in the present example is disposed at a right angle tothis first wall portion. However, alternatively this angle may be anoblique angle. The internal cutting member 7 comprises cutting elements8. In known manner, the cutting member 7 is driven so as to reciprocate.As a result of the cooperation between the cutting elements 8 and thelamellae 3 hairs caught in the hair-entry apertures 4 (gaps) aresevered. The ends of the lamellae 3 extend beyond the second wallportion 6 in such a manner that these projecting ends form rows 9 ofteeth. In the example shown in FIG. 1 a row of teeth has two types ofteeth, namely long teeth 9 ^(a), 9 ^(b), . . . and short teeth 9 ¹, 9 ²,. . . disposed in an alternating arrangement. The long teeth project,for example, 0.8 mm and the short teeth approximately 0.4 mm beyond thesecond wall portion 6. However, it is obviously also possible to have,for example, one short tooth after every two teeth, or the other wayround.

It will now be explained first why in a cutting apparatus having bothlong and short teeth has can be raised and guided into the hair-entryapertures in a better way than a cutting apparatus having teeth whichall have the same length. FIG. 2 shows a detail of the teeth of aprior-art hair-cutting apparatus, in which for the sake of clarity theteeth are shown upside down in, comparison with FIG. 1. An arrow Pindicates the direction of movement of the hair-cutting apparatus overthe skin. The teeth 9 all have the same length. A hair to be severed 10lies comparatively flat on the skin 11. As the hair-cutting apparatus ismoved over the skin the tip 12 of the tooth 9 ^(c) comes into contactwith the hair. A tooth tip is always rounded. Since the hair liescomparatively flat the hair will slip underneath the tooth 9 ^(c) ratherthan enter the hair-entry aperture 4. Although towards its end 10 a thehair 10 is disposed farther from the skin and could be raised by thetooth 9 ^(b), this does not happen because the hair has already beenpressed downward by the tooth 9 ^(c). Only when a hair 13 is in a moreerect position can the tip 14 of the tooth 9 ^(d) slip underneath thehair, subsequently lift the hair and guide it into the hair-entryaperture 4.

FIG. 3 show a situation similar to that in FIG. 2 but now there are longteeth 9 ^(a), 9 ^(b), . . . and short teeth 9 ¹, 9 ² . . . arrangedalternately as in accordance with the invention. FIG. 3, similarly toFIG. 2, shows a hair 10 which lies comparatively flat. Since the shorttooth 9 ² is more receded the hair does not first come into contact withthe short tooth 9 ² but with the adjacent long tooth 9 ^(b). Since thetooth 9 ^(b) is farther away from the root 15 of the hair 10 (the hairis slightly inclined), the distance from the hair to the skin at thelocation of the tooth 9 ^(b) is larger, as a result of which the tip 16of the tooth 9 ^(b) can now slip underneath the hair and can raise thishair. Slightly later the short tooth 9 ² ensures that the hair isfurther raised (as indicated in broken lines) and subsequently guides itinto the hair-entry aperture 4. It has been found that in this way morehairs are severed per unit of time. This improves the cuttingperformance and hence the cutting efficiency.

The efficiency can be improved even further by choosing the correct apexangle for the teeth, i.e. the angle β₁ between the cutting face 5 andthe wall portion 17 of the tooth 9 ^(a), 9 ^(b), . . . and the angle β₂between the cutting face 5 and the wall portion 18 of the tooth 9 ¹, 9², . . . (FIG. 4). On the one hand, sharp-pointed tooth tips will morereadily slip underneath the hairs than less sharp tooth tips but, on theother hand, sharp tooth tips are more likely to irritate the skin thanless sharp teeth. A greater number of sharp teeth also give rise to moreirritation. Therefore, as is shown in FIG. 5, said apex angle β₁ for along tooth 9 ^(a), 9 ^(b), . . . is smaller than the apex angle β₂ for ashort tooth 9 ¹, 9 ², . . . The angle β₂ for the short teeth can belarger because the short teeth serve for further raised the hairsalready raised.

The rounding of a tooth tip also influences the irritating effect of theteeth on the skin (FIG. 5). A smaller radius of rounding is more likelyto lead to irritation than a large radius. However, a tooth having asmaller rounding can more easily slip underneath a hair. Preferably, theradius R₂ of rounding of the short teeth 9 ¹, 9 ², . . . is smaller thanthe radius R₁ of rounding of the long teeth 9 ^(a), 9 ^(b), . . . Anirritating effect of short teeth is small because the skin which passesunderneath the short tooth has already been pressed away slightly by thelong teeth.

In order to minimize an irritating effect during shaving the ends 20, 21of the teeth are slightly beveled (FIG. 6).

Obviously, the invention can also be applied to a hair-cutting apparatushaving a row of teeth at only one side, as is customary in a shaverhaving a slide-out or swing-out trimmer at one side.

FIG. 7 shows another example of a hair-cutting apparatus in the form ofa triple-head rotary shaver having circular shaving heads 22. Thelamellae 3 with the hair-entry apertures between them are oriented insubstantially radial directions. All the ends of the lamellae form teethhaving different projecting lengths. In the present example two shortteeth 9 ¹, 9 ² are disposed between two long teeth 9 ^(a), 9 ^(b).

What is claimed is:
 1. A cutting apparatus having an external cuttingmember and an internal cutting member which is drivable relative to theexternal cutting member, which external cutting member is formed by afirst wall portion, which constitutes a cutting face, and at least asecond wall portion, which is disposed at an angle with respect to thefirst wall portion, which first wall portion has lamellae between whichelongate hair-entry apertures are situated, ends of the lamellaeextending beyond the second wall portion in such a manner that the endsof the lamellae form a row of teeth for raising hairs to be severedbetween the cutting members, wherein the teeth have different projectinglengths with respect to the second wall portion and comprise a firsttype of teeth and a second type of teeth, the first type of teeth beinglong teeth having a larger projecting length when compared to the secondtype of teeth, and wherein, viewed in a longitudinal section of alamella, an apex angle of a tooth of the first type is smaller than anapex angle of a tooth of the second type.
 2. A cutting apparatus havingan external cutting member and an internal cutting member which isdrivable relative to the external cutting member, which external cuttingmember is formed by a first wall portion, which constitutes a cuttingface, and at least a second wall portion, which is disposed at an anglewith respect to the first wall portion, which first wall portion haslamellae between which elongate hair-entry apertures are situated, endsof the lamellae extending beyond the second wall portion in such amanner that the ends of the lamellae form a row of teeth for raisinghairs to be severed between the cutting members, wherein the teeth havedifferent projecting lengths with respect to the second wall portion andcomprise a first type of teeth and a second type of teeth, the firsttype of teeth being long teeth having a larger projecting length whencompared to the second type of teeth, and wherein viewed in alongitudinal section of a lamella, the tooth tips of the teeth of thesecond type have a smaller radius of rounding than the tooth tips of theteeth of the first type.